Plants such as trees are susceptible to various diseases and afflictions which may be treated by appropriate treatment fluids including nutrients, insecticides, fungicides, growth hormones, regulators and the like. In some cases, such treatment chemicals can be applied to the soil where the roots are located or sprayed onto the leaves of the plant.
Such methods can be inefficient and are environmentally undesirable in that run-off of treatment fluids can pollute surrounding land or water systems. It is generally more efficient to administer a treatment fluid to a plant such as a tree by directly inoculating the trunk or branches of the tree and many different injection methods have been developed for this purpose. Direct injection of a treatment fluid into plant tissue also poses less of an environmental hazard.
Tree injection devices are known and are described, for example, in U.K. Patent No. 2234148 which discloses a closed plastics tube filled with treatment fluid and having a drivable end closure with a line of weakness. In U.S. Pat. No. 4,896,454 there is described an inclined tube secured by a bracket to a tree trunk with a first resilient bushing located in the tube lower end and sealed with a second bushing located in the tube upper end and sealing the upper end. Liquid can be injected into the tree by a hypodermic needle which is passed through the upper end bushing. In U.K. Patent No. 2213032 there is described a method for injecting a tree with a liquid chemical which uses an injection tube and flexible container to feed the chemical at a low pressure. The container is made in the form of an elastic tube which is filled with the liquid chemical and attached by one end to the injection tube with the other end closed. In U.S. Pat. No. 4,698,935 and No. 4,766,659 there is described a tree injector inserted through a mass of sealable material such as a silicone which is carried by the rearward end portion of the cartridge and accessible externally thereof. In Australian Patent No. 608767 there is described an injector for use in the subcutaneous injection of fluid into a plant which is of a syringe-like configuration including an outlet nozzle and a plunger reciprocally slidable in an internal chamber of the injector. In Australian Patent Application No. 74861/87, there is described a tree dosing device having a moveable piston actuated by a trigger comprising a blade and a fluid injector. French Patent No. 2422322 refers to a ligneous plant injection system with fluid delivered by a syringe or tube pressed into sapwood.
U.S. Pat. No. 4,164,093 described an injector for branches of tress having a self locking wrench used to clamp a disposable syringe tip against a branch. In U.S. Pat. No. 4,011,685 there is described a tree injection system comprising a syringe including a barrel with an axially slidable piston and piston rod. A transverse bore leads into the barrel from a reservoir which extends vertically above the barrel. When the piston is fully withdrawn, liquid from the reservoir enters the barrel. When the piston is advanced, the transverse bore is sealed off while the liquid in the barrel is discharged via a needle at one end of the barrel. A check valve is included adjacent the needle.
A tree treatment capsule is described in Australian Patent No. 594875. The capsule is insertable as a unit into a bore of a tree and is frangible so that upon application of an impact force chemical agent contained within the capsule can mix with the sap of the tree. Australian Patent No. 570799 describes a plant treatment means comprising an unpressurised reservoir intended to contain a plant treatment agent and adapted to be fixed to a plant stem and having at least one probe able to penetrate the epidermis of the plant.
The main disadvantages of the prior art referred to above is that they provide limited sealing between the injection device and the tree tissue, thereby severely limiting injection pressure and consequently providing relatively slow injection rates. Furthermore, most if not all of the prior art devices seal against the phloem tissue (soft growth) and expose the cambium layer to the injected chemicals and hydraulic pressure. This can cause hydraulic separation of the cambium and phloem layers from the xylem and enough physical and chemical damage to kill large sections of the cambium and phloem around the injection sight.
None of the prior art provides the ability to inject multiple chemical solutions via the same hole without significant time delays and consequent increased costs.